U.S. patent number 10,171,175 [Application Number 15/857,019] was granted by the patent office on 2019-01-01 for method and apparatus for despreading in optical domain.
This patent grant is currently assigned to Huawei Technologies Co., Ltd.. The grantee listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Liming Fang, Meng Sui, Xiaofeng Zhang, Lei Zhou.
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United States Patent |
10,171,175 |
Fang , et al. |
January 1, 2019 |
Method and apparatus for despreading in optical domain
Abstract
An apparatus for despreading in an optical domain configured to
split a received optical signal into a first optical signal and a
second optical signal, perform phase deflection on the second
optical signal, output a third optical signal, perform phase
deflection on the first optical signal and the third optical
signal, output a fourth optical signal and a fifth optical signal
to a balanced receiver, and superimpose the fourth optical signal
and the fifth optical signal to generate a first electrical signal.
A multiplication operation in conventional code division multiple
access (CDMA) despreading is transferred from an electrical domain
to an optical domain such that a chip rate can be easily raised to
20 gigahertz (GHz) or even to 25 GHz, a maximum rate of 100
gigabits per second (Gbps) can be provided in a single wavelength,
and a user requirement for high bandwidth can be met.
Inventors: |
Fang; Liming (Shenzhen,
CN), Zhou; Lei (Shenzhen, CN), Sui;
Meng (Shenzhen, CN), Zhang; Xiaofeng (Shenzhen,
CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
N/A |
CN |
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Assignee: |
Huawei Technologies Co., Ltd.
(Shenzhen, CN)
|
Family
ID: |
57607442 |
Appl.
No.: |
15/857,019 |
Filed: |
December 28, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180145767 A1 |
May 24, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CN2015/082882 |
Jun 30, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B
10/60 (20130101); H04B 10/6162 (20130101); H04B
10/25891 (20200501); H04J 13/16 (20130101) |
Current International
Class: |
H04B
10/00 (20130101); H04B 10/61 (20130101); H04B
10/60 (20130101); H04B 10/25 (20130101); H04J
13/16 (20110101) |
Field of
Search: |
;398/115 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101102162 |
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Jan 2008 |
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CN |
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101283528 |
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Oct 2008 |
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CN |
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102882631 |
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Jan 2013 |
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CN |
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104266752 |
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Jan 2015 |
|
CN |
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2256959 |
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Dec 2010 |
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EP |
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2006001362 |
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Jan 2006 |
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WO |
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2009102164 |
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Aug 2009 |
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WO |
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Other References
Machine Translation and Abstract of Chinese Publication No.
CN104266752, Jan. 7, 2015, 7 pages. cited by applicant .
Foreign Communication From a Counterpart Application, European
Application No. 15896777.8, Extended European Search Report dated
Jun. 6, 2018, 7 pages. cited by applicant .
Machine Translation and Abstract of Chinese Publication No.
CN101102162, Jan. 9, 2008, 12 pages. cited by applicant .
Machine Translation and Abstract of Chinese Publication No.
CN102882631, Jan. 16, 2013, 25 pages. cited by applicant .
Gupta, G., et al: "Over 100km Bidirectional, Multi-channels COF-PON
without Optical Amplifier," PDP51, 2006, 3 pages. cited by
applicant .
Foreign Communication From a Counterpart Application, PCT
Application No. PCT/CN2015/082882, English Translation of
International Search Report dated Apr. 1, 2016, 2 pages. cited by
applicant .
Foreign Communication From a Counterpart Application, PCT
Application No. PCT/CN2015/082882, English Translation of Written
Opinion dated Apr. 1, 2016, 7 pages. cited by applicant.
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Primary Examiner: Sedighian; M. R.
Attorney, Agent or Firm: Conley Rose, P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of International Patent
Application No. PCT/CN2015/082882 filed on Jun. 30, 2015, which is
hereby incorporated by reference in its entirety.
Claims
What is claimed is:
1. An apparatus for despreading in an optical domain, comprising:
an optical splitter configured to: split a received optical signal
into a first optical signal and a second optical signal; output the
first optical signal to an optical coupler; and output the second
optical signal to an optical modulator, wherein the optical
modulator is coupled to the optical splitter and is configured to:
perform field modulation on the second optical signal to obtain a
third optical signal; and output the third optical signal to the
optical coupler, wherein a phase difference between the third
optical signal and the first optical signal is a first difference,
wherein the optical coupler is coupled to the optical splitter and
the optical modulator and is configured to: perform phase
deflection processing on the first optical signal and the third
optical signal to obtain a fourth optical signal and a fifth
optical signal respectively; and output the fourth optical signal
and the fifth optical signal to a balanced receiver, wherein the
balanced receiver is coupled to the optical coupler and is
configured to: superimpose electrical signals obtained by
converting the fourth optical signal and the fifth optical signal
to generate a first electrical signal; and output the first
electrical signal to an accumulator, and wherein the accumulator is
coupled to the balanced receiver and is configured to accumulate
the first electrical signal in each code word period.
2. The apparatus according to claim 1, wherein the optical
modulator is further configured to perform the field modulation on
the second optical signal according to a local code word.
3. The apparatus according to claim 1, wherein a polarization
direction of the first optical signal is the same as a polarization
direction of the third optical signal.
4. The apparatus according to claim 1, wherein when performing the
phase deflection processing on the first optical signal and the
third optical signal and before outputting the fourth optical
signal and the fifth optical signal to the balanced receiver, the
optical coupler is further configured to: deflect a phase of the
first optical signal by the first difference; superimpose the first
optical signal and the third optical signal to obtain the fourth
optical signal; deflect a phase of the third optical signal by the
first difference; and superimpose the third optical signal and the
first optical signal to obtain the fifth optical signal.
5. The apparatus according to claim 1, wherein the balanced
receiver comprises: a first photodiode (PD) configured to: receive
the fourth optical signal; and convert the fourth optical signal
into a second electrical signal; a second PD configured to: receive
the fifth optical signal; and convert the fifth optical signal into
a third electrical signal; and a summator coupled to the first PD
and the second PD and configured to superimpose the second
electrical signal and the third electrical signal to obtain the
first electrical signal.
6. The apparatus according to claim 5, further comprising a phase
demodulator, wherein one end of the phase demodulator is coupled to
the accumulator, wherein the other end of the phase demodulator is
coupled to the optical modulator, and wherein the phase demodulator
is configured to adjust a phase of a code word of the second
optical signal to align the code word of the second optical signal
with a code word of the received optical signal.
7. The apparatus according to claim 1, wherein the first difference
is .pi./2.
8. An apparatus for despreading in an optical domain, comprising: a
first polarization beam splitter (PBS) configured to: split a
received optical signal into a first optical signal and a second
optical signal, wherein polarization directions of the first
optical signal and the second optical signal are perpendicular to
each other; output the first optical signal to a first optical
coupler; and output the second optical signal to a second optical
coupler; a local oscillator laser configured to emit a local
oscillator optical signal; a second PBS coupled to the local
oscillator laser and configured to split the local oscillator
optical signal into a third optical signal and a fourth optical
signal, wherein polarization directions of the third optical signal
and the fourth optical signal are perpendicular to each other; a
first optical modulator coupled to the second PBS and configured
to: perform field modulation on the third optical signal to
generate a fifth optical signal; and output the fifth optical
signal to the first optical coupler, wherein a phase difference
between the fifth optical signal and the first optical signal is a
first difference; a second optical modulator coupled to the second
PBS and configured to: perform the field modulation on the fourth
optical signal to generate a sixth optical signal; and output the
sixth optical signal to the second optical coupler, wherein a phase
difference between the sixth optical signal and the second optical
signal is the first difference, wherein the first optical coupler
coupled to the first PBS and the first optical modulator and
configured to: perform phase deflection on the first optical signal
and the fifth optical signal to obtain a seventh optical signal and
an eighth optical signal respectively; and output the seventh
optical signal and the eighth optical signal, wherein the second
optical coupler coupled to the first PBS and the second optical
modulator and configured to: perform the phase deflection on the
second optical signal and the sixth optical signal to obtain a
ninth optical signal and a tenth optical signal respectively; and
output the ninth optical signal and the tenth optical signal; a
first balanced receiver coupled to the first optical coupler and
configured to: superimpose electrical signals obtained by
converting the seventh optical signal and the eighth optical
signal; and output a first electrical signal; a second balanced
receiver coupled to the second optical coupler and configured to:
superimpose electrical signals obtained by converting the ninth
optical signal and the tenth optical signal; and output a second
electrical signal; and an accumulator coupled to the first balanced
receiver and the second balanced receiver and configured to
accumulate the first electrical signal and the second electrical
signal in each code word period.
9. The apparatus according to claim 8, further comprising a first
device coupled to the first balanced receiver and the second
balanced receiver and configured to perform a square operation on
the first electrical signal and the second electrical signal.
10. The apparatus according to claim 8, wherein when performing the
phase deflection on the first optical signal and the fifth optical
signal and before outputting the seventh optical signal and the
eighth optical signal, the first optical coupler is further
configured to: deflect a phase of the fifth optical signal by the
first difference; superimpose the fifth optical signal and the
first optical signal to obtain the seventh optical signal; deflect
a phase of the first optical signal by the first difference; and
superimpose the first optical signal and the fifth optical signal
to obtain the eighth optical signal.
11. The apparatus according to claim 8, wherein when performing the
phase deflection on the second optical signal and the sixth optical
signal and before outputting the ninth optical signal and the tenth
optical signal, the second optical coupler is further configured
to: deflect a phase of the sixth optical signal by the first
difference; superimpose the sixth optical signal and the second
optical signal to obtain the ninth optical signal; deflect a phase
of the second optical signal by the first difference; and
superimpose the second optical signal and the sixth optical signal
to obtain the tenth optical signal.
12. The apparatus according to claim 8, wherein the first balanced
receiver comprises: a first photodiode (PD) configured to: receive
the seventh optical signal; and convert the seventh optical signal
into a third electrical signal; a second PD configured to: receive
the eighth optical signal; and convert the eighth optical signal
into a fourth electrical signal; and a first summator coupled to
the first PD and the second PD and configured to: superimpose the
third electrical signal and the fourth electrical signal to obtain
the first electrical signal; and output the first electrical
signal.
13. The apparatus according to claim 8, further comprising a phase
demodulator configured to adjust a phase of a code word of the
local oscillator optical signal to align the code word of the local
oscillator optical signal with a code word of the received optical
signal.
14. The apparatus according to claim 8, wherein the first
difference is .pi./2.
15. A method for despreading in an optical domain, comprising:
splitting a received optical signal into a first optical signal and
a second optical signal; performing field modulation on the second
optical signal to obtain a third optical signal, wherein a phase
difference between the third optical signal and the first optical
signal is a first difference; performing phase deflection on the
third optical signal and the first optical signal to obtain a
fourth optical signal and a fifth optical signal respectively;
superimposing electrical signals obtained by converting the fourth
optical signal and the fifth optical signal to generate a first
electrical signal; and accumulating the first electrical signal in
each code word period.
16. The method according to claim 15, wherein performing the field
modulation comprises performing the field modulation on the first
optical signal according to a local code word.
17. The method according to claim 15, wherein a polarization
direction of the first optical signal is the same as a polarization
direction of the third optical signal.
18. The method according to claim 15, wherein performing the phase
deflection on the third optical signal and the first optical signal
comprises: deflecting a phase of the third optical signal by the
first difference; superimposing the third optical signal and the
first optical signal to obtain the fourth optical signal;
deflecting a phase of the first optical signal by the first
difference; and superimposing the first optical signal and the
third optical signal to obtain the fifth optical signal.
19. The method according to claim 15, wherein superimposing the
electrical signals comprises: converting the fourth optical signal
into a second electrical signal; converting the fifth optical
signal into a third electrical signal; and superimposing the second
electrical signal and the third electrical signal to obtain the
first electrical signal.
20. The method according to claim 15, further comprising adjusting
a phase of a code word of the second optical signal to align the
code word of the second optical signal with a code word of the
received optical signal.
Description
TECHNICAL FIELD
The present disclosure relates to the communications field, and in
particular, to a method and a device for despreading in an optical
domain.
BACKGROUND
As users' demand for bandwidth continuously increases, a
conventional copper wire broadband access system is confronted with
more bandwidth bottlenecks. At the same time, an optical fiber
communications technology with a massive bandwidth capacity is
increasingly mature, application costs are reduced year by year,
and an optical fiber access network becomes a strong competitor of
a next-generation broadband access network. In particular, a
passive optical network (PON) system is more competitive. FIG. 1
shows a common network structure of the PON system. The PON system
generally includes one optical line terminal (OLT) that is located
in a central office, one optical distribution network (ODN) that is
used for splitting/coupling or multiplexing/demultiplexing, and
several optical network unit (ONUs) (designated as ONU 1, ONU 2 and
ONU n).
A Code Division Multiple Access (CDMA) technology is a mature
wireless communications technology developed based on a branch of a
digital technology, that is, a spread spectrum communications
technology. A principle of the CDMA technology is based on the
spread spectrum technology, that is, modulating to-be-transmitted
information data with specific signal bandwidth using a high-speed
code word whose bandwidth is far higher than the signal bandwidth
in order to expand bandwidth of an original data signal, and then
sending the signal that undergoes carrier modulation. A receive end
uses completely the same code word to perform related processing on
the received broadband signal, and changes the broadband signal
into a narrowband signal of the original information data, that is,
despreading in order to implement information communication.
In a CDMA access manner, users do not need to maintain
synchronization, multiple users share an entire channel, all the
users may access a same channel at any time without complex access
control, and a service does not need to wait a long time for
transmission. Therefore, the CDMA access manner becomes an ideal
multiple access manner, and the CDMA technology makes a great
success in mobile communication. In other approaches, CDMA access
control is used in an optical fiber access network, and the CDMA
technology is usually used in an electrical domain.
This solution has a disadvantage that because an electronic rate is
limited, a rate obtained after spreading is limited, and this
manner can hardly meet a requirement of development of a future
high-speed image service such as a video on demand (VOD) and a
high-definition television (TV) (HDTV).
SUMMARY
Embodiments of the present disclosure provide a method and an
apparatus for despreading in an optical domain in order to resolve
a technical problem that a rate cannot meet a user requirement.
To achieve the foregoing objective, the following technical
solutions are used in the embodiments of the present
disclosure.
According to a first aspect, an apparatus for despreading in an
optical domain is provided, where the apparatus includes an optical
splitter configured to split a received optical signal into a first
optical signal and a second optical signal, where the first optical
signal is input to an optical coupler, and the second optical
signal is input to an optical modulator, the optical modulator
configured to perform field modulation on the second optical
signal, and output a third optical signal, where a phase difference
between the third optical signal and the first optical signal is a
first difference, and the third optical signal is input to the
optical coupler, the optical coupler configured to perform phase
deflection processing on the first optical signal and the third
optical signal, and output a fourth optical signal and a fifth
optical signal to a balanced receiver, the balanced receiver
configured to superimpose the fourth optical signal and the fifth
optical signal to generate a first electrical signal, and output
the first electrical signal, and an accumulator configured to
accumulate the first electrical signal in each code word
period.
With reference to the first aspect, in a first possible
implementation of the first aspect, the optical modulator performs
field modulation on the second optical signal according to a local
code word.
With reference to the first or the second possible implementation
of the first aspect, a polarization direction of the first optical
signal is the same as a polarization direction of the third optical
signal.
With reference to the first to the third possible implementations
of the first aspect, the optical coupler is configured to perform
phase deflection processing on the first optical signal and the
third optical signal, and output a fourth optical signal and a
fifth optical signal to a balanced receiver, deflect a phase of the
first optical signal by the first difference, and superimposing the
first optical signal and the third optical signal to obtain the
fourth optical signal, and deflect a phase of the third optical
signal by the first difference, and superimposing the third optical
signal and the first optical signal to obtain the fifth optical
signal.
With reference to any one of the first aspect or the possible
implementations of the first aspect, in a fourth possible
implementation of the first aspect, the balanced receiver further
includes a first photodiode (PD), a second PD, and a summator,
where the first PD is configured to receive the fourth optical
signal, and convert the fourth optical signal into a second
electrical signal. The second PD is configured to receive the fifth
optical signal, and convert the fifth optical signal into a third
electrical signal, and the summator is configured to superimpose
the second electrical signal and the third electrical signal to
obtain the first electrical signal.
With reference to any one of the first aspect or the possible
implementations of the first aspect, in a fifth possible
implementation of the first aspect, the apparatus further includes
a phase demodulator, one end is connected to the accumulator, the
other end is connected to the optical modulator, and the phase
demodulator is configured to adjust a phase of a code word of the
second optical signal such that the code word of the second optical
signal is aligned with a code word of the received optical
signal.
With reference to any one of the first aspect or the possible
implementations of the first aspect, in a sixth possible
implementation of the first aspect, the first difference is
.pi./2.
According to a second aspect, an apparatus for despreading in an
optical domain is provided, where the apparatus includes a first
polarization beam splitter (PBS) configured to split a received
optical signal into a first optical signal and a second optical
signal whose polarization directions are perpendicular to each
other, where the first optical signal and the second optical signal
are input to a first optical coupler and a second optical coupler
respectively, a local oscillator laser configured to emit a local
oscillator optical signal, a second PBS configured to split the
local oscillator optical signal into a third optical signal and a
fourth optical signal whose polarization directions are
perpendicular to each other, and a first optical modulator and a
second optical modulator is configured to modulate the third
optical signal and the fourth optical signal respectively to
generate a fifth optical signal and a sixth optical signal, and
input the fifth optical signal and the sixth optical signal to the
first optical coupler and the second optical coupler respectively,
where a polarization state of the fifth optical signal is the same
as a polarization state of the first optical signal, and a phase
difference between the fifth optical signal and the first optical
signal is a first difference, and a polarization state of the sixth
optical signal is the same as a polarization state of the second
optical signal, and a phase difference between the sixth optical
signal and the second optical signal is the first difference, the
first optical coupler is configured to perform phase deflection on
the first optical signal and the fifth optical signal, and output a
seventh optical signal and an eighth optical signal, the second
optical coupler is configured to perform phase deflection on the
second optical signal and the sixth optical signal, and output a
ninth optical signal and a tenth optical signal, a first balanced
receiver is configured to superimpose the seventh optical signal
and the eighth optical signal, and output a first electrical
signal, a second balanced receiver is configured to superimpose the
ninth optical signal and the tenth optical signal, and output a
second electrical signal, and an accumulator is configured to
accumulate the first electrical signal and the second electrical
signal.
With reference to the second aspect, in a first possible
implementation of the second aspect, that the first optical coupler
is configured to perform phase deflection on the first optical
signal and the fifth optical signal, and output a seventh optical
signal and an eighth optical signal includes deflecting a phase of
the fifth optical signal by the first difference, and superimposing
the fifth optical signal and the first optical signal to obtain the
seventh optical signal, deflecting a phase of the first optical
signal by the first difference, and superimposing the first optical
signal and the fifth optical signal to obtain the eighth optical
signal.
With reference to the second aspect or the first possible
implementation of the second aspect, in a second possible
implementation of the second aspect, that the second optical
coupler is configured to perform phase deflection on the second
optical signal and the sixth optical signal, and output a ninth
optical signal and a tenth optical signal includes deflecting a
phase of the sixth optical signal by the first difference,
superimposing the sixth optical signal and the second optical
signal to obtain the ninth optical signal, deflecting a phase of
the second optical signal by the first difference, and
superimposing the second optical signal and the sixth optical
signal to obtain the tenth optical signal.
With reference to any one of the second aspect or the possible
implementations of the second aspect, in a third possible
implementation of the second aspect, the first balanced receiver
further includes a first PD, a second PD, and a first summator,
where the first PD is configured to receive the seventh optical
signal, and convert the seventh optical signal into a third
electrical signal, and the second PD is configured to receive the
eighth optical signal, and convert the eighth optical signal into a
fourth electrical signal, and the first summator is configured to
superimpose the third electrical signal and the fourth electrical
signal, and output the first electrical signal.
With reference to any one of the second aspect or the possible
implementations of the second aspect, in a fourth possible
implementation of the second aspect, the second balanced receiver
further includes a third PD, a fourth PD, and a second summator,
where the third PD is configured to receive the ninth optical
signal, and convert the ninth optical signal into a fifth
electrical signal, the fourth PD is configured to receive the tenth
optical signal, and convert the tenth optical signal into a sixth
electrical signal, and the second summator is configured to
superimpose the fifth electrical signal and the sixth electrical
signal, and output the second electrical signal.
With reference to any one of the second aspect or the possible
implementations of the second aspect, in a fifth possible
implementation of the second aspect, the apparatus further includes
a phase demodulator configured to adjust a phase of a code word of
the local oscillator optical signal such that the code word of the
local oscillator optical signal is aligned with a code word of the
received optical signal.
With reference to any one of the second aspect or the possible
implementations of the second aspect, in a sixth possible
implementation of the second aspect, the apparatus further includes
a first device configured to perform a square operation on the
first electrical signal and the second electrical signal.
With reference to any one of the second aspect or the possible
implementations of the second aspect, in a seventh possible
implementation of the second aspect, the first device is an analog
device, or a digital device such as an analog to digital converter
(ADC).
With reference to any one of the second aspect or the possible
implementations of the second aspect, in a seventh possible
implementation of the second aspect, the first difference is
.pi./2.
According to a third aspect, a method for despreading in an optical
domain is provided, where the method includes splitting a received
optical signal into a first optical signal and a second optical
signal, performing field modulation on the first optical signal to
obtain a third optical signal, where a phase difference between the
third optical signal and the first optical signal is a first
difference, performing phase deflection on the third optical signal
and the first optical signal to obtain a fourth optical signal and
a fifth optical signal, superimposing electrical signals that are
obtained by converting the fourth optical signal and the fifth
optical signal to generate a first electrical signal, and
accumulating the first electrical signal in each code word
period.
With reference to the third aspect, in a first possible
implementation of the third aspect, field modulation is performed
on the first optical signal according to a local code word.
With reference to the third aspect or the first possible
implementation of the third aspect, in a second possible
implementation of the third aspect, a polarization direction of the
first optical signal is the same as a polarization direction of the
third optical signal.
With reference to any one of the third aspect or the possible
implementations of the third aspect, in a third possible
implementation of the third aspect, performing phase deflection on
the third optical signal and the first optical signal to obtain a
fourth optical signal and a fifth optical signal includes
deflecting a phase of the third optical signal by the first
difference, superimposing the third optical signal and the first
optical signal to obtain the fourth optical signal, deflecting a
phase of the first optical signal by the first difference, and
superimposing the first optical signal and the third optical signal
to obtain the fifth optical signal.
With reference to any one of the third aspect or the possible
implementations of the third aspect, in a fourth possible
implementation of the third aspect, superimposing electrical
signals that are obtained by converting the fourth optical signal
and the fifth optical signal in order to generate a first
electrical signal includes converting the fourth optical signal
into a second electrical signal, converting the fifth optical
signal into a third electrical signal, and superimposing the second
electrical signal and the third electrical signal to obtain the
first electrical signal.
With reference to any one of the third aspect or the possible
implementations of the third aspect, in a fifth possible
implementation of the third aspect, the method further includes
adjusting a phase of a code word of the second optical signal such
that the code word of the second optical signal is aligned with a
code word of the received optical signal.
With reference to any one of the third aspect or the possible
implementations of the third aspect, in a sixth possible
implementation of the third aspect, the first difference is
.pi./2.
According to a fourth aspect, a method for despreading in an
optical domain is provided, where the method includes splitting a
received optical signal into a first optical signal and a second
optical signal whose polarization directions are perpendicular to
each other, splitting a local oscillator optical signal emitted by
a local oscillator laser into a third optical signal and a fourth
optical signal whose polarization directions are perpendicular to
each other, modulating the third optical signal and the fourth
optical signal to generate a fifth optical signal and a sixth
optical signal respectively, performing phase deflection on the
first optical signal and the fifth optical signal, to obtain a
seventh optical signal and an eighth optical signal, performing
phase deflection on the second optical signal and the sixth optical
signal, to obtain a ninth optical signal and a tenth optical
signal, superimposing electrical signals obtained by converting the
seventh optical signal and the eighth optical signal, to obtain a
first electrical signal, superimposing electrical signals obtained
by converting the ninth optical signal and the tenth optical signal
to obtain a second electrical signal, superimposing the first
electrical signal and the second electrical signal to obtain a
third electrical signal, and accumulating the third electrical
signal in each code word period.
With reference to the fourth aspect, in a first possible
implementation of the fourth aspect, performing phase deflection on
the first optical signal and the fifth optical signal to obtain a
seventh optical signal and an eighth optical signal includes
deflecting a phase of the fifth optical signal by the first
difference, superimposing the fifth optical signal and the first
optical signal to obtain the seventh optical signal, deflecting a
phase of the first optical signal by the first difference, and
superimposing the first optical signal and the fifth optical signal
to obtain the eighth optical signal.
With reference to the fourth aspect or the first possible
implementation of the fourth aspect, in a second possible
implementation of the fourth aspect, performing phase deflection on
the second optical signal and the sixth optical signal to obtain a
ninth optical signal and a tenth optical signal includes deflecting
a phase of the sixth optical signal by the first difference,
superimposing the sixth optical signal and the second optical
signal to obtain the ninth optical signal, deflecting a phase of
the second optical signal by the first difference, and
superimposing the second optical signal and the sixth optical
signal to obtain the tenth optical signal.
With reference to any one of the fourth aspect or the possible
implementations of the fourth aspect, in a third possible
implementation of the fourth aspect, superimposing electrical
signals obtained by converting the seventh optical signal and the
eighth optical signal includes converting the seventh optical
signal into a fourth electrical signal, converting the eighth
optical signal into a fifth electrical signal, and superimposing
the fourth electrical signal and the fifth electrical signal to
obtain the first electrical signal.
With reference to any one of the fourth aspect or the possible
implementations of the fourth aspect, in a fourth possible
implementation of the fourth aspect, superimposing electrical
signals obtained by converting the ninth optical signal and the
tenth optical signal includes converting the ninth optical signal
into a sixth electrical signal, converting the tenth optical signal
into a seventh electrical signal, and superimposing the sixth
electrical signal and the seventh electrical signal to obtain the
second electrical signal.
With reference to any one of the fourth aspect or the possible
implementations of the fourth aspect, in a fifth possible
implementation of the fourth aspect, the method further includes
adjusting a phase of a code word of the local oscillator optical
signal such that the code word of the local oscillator optical
signal is aligned with a code word of the received optical
signal.
With reference to any one of the fourth aspect or the possible
implementations of the fourth aspect, in a sixth possible
implementation of the fourth aspect, the first difference is
.pi./2.
In the embodiments of the present disclosure, a multiplication
operation in conventional CDMA despreading is transferred from an
electrical domain to an optical domain, and only an accumulation
operation is performed in the electrical domain such that a chip
rate can be easily raised to 20 gigahertz (GHz), or even to 25 GHz,
a maximum rate of 100 gigabits per second (Gbps) can be provided in
a single wavelength, and a user's requirement for high bandwidth
can be met. In addition, the apparatus provided in the embodiments
of the present disclosure requires lower costs than that required
in the other approaches.
BRIEF DESCRIPTION OF DRAWINGS
To describe the technical solutions in the embodiments of the
present disclosure more clearly, the following briefly describes
the accompanying drawings required for describing the embodiments.
The accompanying drawings in the following description show merely
some embodiments of the present disclosure, and a person of
ordinary skill in the art may still derive other drawings from
these accompanying drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a PON;
FIG. 2 is a schematic structural diagram of an apparatus for
despreading in an optical domain according to an embodiment of the
present disclosure;
FIG. 3A is a schematic structural diagram of an apparatus for
despreading in an optical domain according to another embodiment of
the present disclosure;
FIG. 3B is a schematic structural diagram of an apparatus for
despreading in an optical domain according to still another
embodiment of the present disclosure;
FIG. 3C is a schematic structural diagram of an apparatus for
despreading in an optical domain according to yet another
embodiment of the present disclosure;
FIG. 4 is a schematic flowchart diagram of steps in a method for
despreading in an optical domain according to an embodiment of the
present disclosure; and
FIG. 5 is a schematic flowchart diagram of steps in a method for
despreading in an optical domain according to another embodiment of
the present disclosure.
DESCRIPTION OF EMBODIMENTS
The following clearly and describes the technical solutions in the
embodiments of the present disclosure with reference to the
accompanying drawings in the embodiments of the present disclosure.
The described embodiments are merely some but not all of the
embodiments of the present disclosure. All other embodiments
obtained by a person of ordinary skill in the art based on the
embodiments of the present disclosure without creative efforts
shall fall within the protection scope of the present
disclosure.
Embodiment 1
As shown in FIG. 2, an embodiment of the present disclosure
provides an apparatus 200 for despreading in an optical domain, and
the apparatus 200 includes an optical splitter 201, an optical
coupler 202, an optical modulator 203, and a balanced receiver
204.
The optical splitter 201 is configured to split a received optical
signal into a first optical signal and a second optical signal, the
first optical signal is input to the optical coupler 202, and the
second optical signal is input to the optical modulator 203.
The optical modulator 203 is configured to perform field modulation
on the second optical signal, and output a third optical signal,
where a phase difference between the third optical signal and the
first optical signal is a first difference, and the third optical
signal is also input to the optical coupler 202. It should be noted
that the optical modulator 203 has a phase deflection function such
that a difference between a phase of the third optical signal and a
phase of the first optical signal or a phase of the second optical
signal is the first difference. In addition, the modulation
mentioned herein is optical field modulation.
Optionally, the field modulation means to perform field modulation
on the second optical signal according to a local code word. The
local code word is a code word corresponding to a ready-to-receive
path or user.
Preferably, the first difference is .pi./2.
Optionally, the first difference may be .pi./4, .pi./16, or
.pi./8.
For example, on a transmit side, code words corresponding to user 1
to user n are respectively code 1 to code n. The local code word is
a code word corresponding to the user on a receive side. For
example, for the user 1, a local code word is the code 1, and for
the user n, a local code word is the code n. In FIG. 2, the local
code word is marked as CL.
The optical coupler 202 is configured to perform phase deflection
on the first optical signal and the third optical signal, and
output a fourth optical signal and a fifth optical signal, where
the fourth optical signal and the fifth optical signal are
separately input to the balanced receiver 204.
The balanced receiver 204 is configured to superimpose electrical
signals that are obtained by converting the fourth optical signal
and the fifth optical signal to generate a first electrical signal,
and output the first electrical signal.
Optionally, a polarization direction of the first optical signal is
the same as a polarization direction of the third optical
signal.
Further, the optical coupler 202 is configured to deflect a phase
of the first optical signal by the first difference, and
superimpose the first optical signal and the third optical signal
to obtain the fourth optical signal, and deflect a phase of the
third optical signal by the first difference, and superimpose the
third optical signal and the first optical signal to obtain the
fifth optical signal.
Further, the balanced receiver 204 further includes a first PD 2041
configured to receive the fourth optical signal, and convert the
fourth optical signal into a second electrical signal, a second PD
2042 configured to receive the fifth optical signal, and convert
the fifth optical signal into a third electrical signal, and a
summator 2043 configured to superimpose the second electrical
signal and the third electrical signal to obtain the first
electrical signal.
It should be noted that the superimposing herein may be a
subtractive operation, or may be an addition operation.
Optionally, the apparatus 200 further includes an accumulator 205.
The accumulator 205 is coupled to the balanced receiver 204, and is
configured to accumulate, in each code word period, the first
electrical signal that is output by the balanced receiver 204, and
output an accumulation result.
It should be noted that the code word period is code word duration,
or may be interpreted as a code word length.
Optionally, the apparatus 200 further includes a phase demodulator
206, where one end is connected to the accumulator 205, the other
end is connected to the optical modulator 203, and the phase
demodulator 206 is configured to adjust a phase of a code word of
the second optical signal such that the code word of the second
optical signal is aligned with a code word of the received optical
signal.
In this embodiment of the present disclosure, a high
signal-to-noise ratio SNR can be obtained by means of coherent
optical receiving. In addition, accumulation is performed only in
an electrical domain, and multiplication is transferred to an
optical domain such that a chip rate can be easily raised to 20
GHz, or even to 25 GHz. In addition, the apparatus 200 provided in
this embodiment of the present disclosure requires lower costs than
that required in the other approaches.
Embodiment 2
As shown in FIG. 3A, another embodiment of the present disclosure
provides an apparatus 300 for despreading in an optical domain, and
the apparatus 300 includes a first PBS 301, a first optical coupler
302, a second optical coupler 303, a local oscillator laser 304, a
second PBS 305, a first optical modulator 306, a second optical
modulator 307, a first balanced receiver 308, a second balanced
receiver 309, and an accumulator 310.
The first PBS 301 is configured to split a received optical signal
into two optical signals whose polarization directions are
perpendicular to each other, where the two signals are denoted as a
first optical signal and a second optical signal, and output the
two optical signals to the first optical coupler 302 and the second
optical coupler 303 respectively.
The local oscillator laser 304 is configured to emit a local
oscillator optical signal, where the emitted local oscillator
optical signal is split by the second PBS 305 into two optical
signals whose polarization directions are perpendicular to each
other, the two signals are denoted as a third optical signal and a
fourth optical signal, and are input to the first optical modulator
306 and the second optical modulator 307 respectively.
The first optical modulator 306 is configured to modulate the third
optical signal to generate a fifth optical signal, and input the
fifth optical signal to the first optical coupler 302. The
modulation means to modulate strength of the optical signal, and a
phase difference between the fifth optical signal and the first
optical signal is a first difference. It should be noted that a
phase of the local oscillator optical signal generated by the local
oscillator laser 304 may be the same as a phase of the first
optical signal, or a difference between a phase of the local
oscillator optical signal and a phase of the first optical signal
may be a first difference. If the phase of the local oscillator
optical signal is the same as the phase of the first optical
signal, when modulating the third optical signal, the first optical
modulator 306 needs to deflect a phase of the third optical signal
such that a difference between a phase of the fifth optical signal
and the phase of the first optical signal is the first difference.
That is, in this case, the first optical modulator 306 not only
needs to perform strength modulation on the third optical signal,
but also needs to perform phase deflection on the third optical
signal. If the difference between the phase of the local oscillator
optical signal and the phase of the first optical signal is the
first difference, a difference between a phase of the third optical
signal and the phase of the first optical signal is the first
difference, and the phase difference between the fifth optical
signal and the first optical signal is the first difference. In
this case, the first optical modulator 306 does not need to deflect
the phase of the third optical signal, and only needs to modulate
the third optical signal.
Preferably, the first difference is .pi./2.
Optionally, the first difference may be .pi./4, .pi./16, or
.pi./8.
The second optical modulator 307 is configured to modulate the
fourth optical signal, to generate a sixth optical signal, and
input the sixth optical signal to the second optical coupler 303. A
phase difference between the sixth optical signal and the second
optical signal is the first difference. It should be noted that the
phase of the local oscillator optical signal generated by the local
oscillator laser 304 may be the same as a phase of the second
optical signal, or a difference between the phase of the local
oscillator optical signal and a phase of the second optical signal
may be the first difference. If the phase of the local oscillator
optical signal is the same as the phase of the second optical
signal, when modulating the fourth optical signal, the second
optical modulator 307 needs to deflect a phase of the fourth
optical signal such that a difference between a phase of the sixth
optical signal and the phase of the second optical signal is the
first difference. That is, in this case, the second optical
modulator 307 not only needs to perform strength modulation on the
fourth optical signal, but also needs to perform phase deflection
on the fourth optical signal. If the difference between the phase
of the local oscillator optical signal and the phase of the second
optical signal is the first difference, a difference between a
phase of the fourth optical signal and the phase of the second
optical signal is the first difference, and the phase difference
between the sixth optical signal and the second optical signal is
the first difference. In this case, the second optical modulator
307 does not need to deflect the phase of the fourth optical
signal, and only needs to modulate the fourth optical signal.
The first optical coupler 302 is configured to perform phase
deflection on the first optical signal and the fifth optical
signal, and output a seventh optical signal and an eighth optical
signal.
The second optical coupler 303 is configured to perform phase
deflection on the second optical signal and the sixth optical
signal, and output a ninth optical signal and a tenth optical
signal.
The first balanced receiver 308 is configured to superimpose
electrical signals obtained by converting the seventh optical
signal and the eighth optical signal, and output a first electrical
signal.
The second balanced receiver 309 is configured to superimpose
electrical signals obtained by converting the ninth optical signal
and the tenth optical signal, and output a second electrical
signal.
The accumulator 310 is configured to accumulate the first
electrical signal and the second electrical signal in each code
word period.
Optionally, as shown in FIG. 3C, an apparatus similar to apparatus
300 shown in FIG. 3A may include a first device 320. As shown in
FIG. 3C, the first device 320 may be an analog device, or may be a
digital device, for example, an ADC.
The first device 320 is configured to perform a square operation on
the first electrical signal and the second electrical signal.
Further, when the first device 320 is an analog device, the first
electrical signal and the second electrical signal are input to two
input interfaces of an analog multiplier in order to complete a
square operation.
When the first device 320 is a digital device, the signals are
first transferred to a digital domain using the ADC, and then a
square operation is directly performed using a digital signal
processor (DSP).
It should be noted that for the square operation performed on the
electrical signals, reference may be made to a solution provided in
the other approaches, and details are not described herein.
Optionally, in this embodiment of the present disclosure, a first
device may be disposed on a transmit side as shown in FIG. 3B. For
example, as shown in FIG. 3A, after a square operation is performed
on an electrical signal of a user, encoding is then performed. In
this solution, a first device does not need to be disposed on a
receive side.
Further, based on FIG. 3A, the first optical coupler 302 is
configured to deflect the phase of the fifth optical signal by the
first difference, superimpose the fifth optical signal and the
first optical signal to obtain the seventh optical signal, deflect
the phase of the first optical signal by the first difference, and
superimpose the first optical signal and the fifth optical signal
to obtain the eighth optical signal.
Further, the second optical coupler 303 is configured to deflect
the phase of the sixth optical signal by the first difference,
superimpose the sixth optical signal and the second optical signal
to obtain the ninth optical signal, deflect the phase of the second
optical signal by the first difference, and superimpose the second
optical signal and the sixth optical signal to obtain the tenth
optical signal.
Further, the first balanced receiver 308 includes a PD 3081, a PD
3082, and a summator 3083.
The PD 3081 is configured to receive the seventh optical signal,
and convert the seventh optical signal into a third electrical
signal.
The PD 3082 is configured to receive the eighth optical signal, and
convert the eighth optical signal into a fourth electrical
signal.
The summator 3083 is configured to superimpose the third electrical
signal and the fourth electrical signal, and output the first
electrical signal.
It should be noted that the superimposing may be a subtractive
operation, or may be an addition operation.
Further, the second balanced receiver 309 includes a PD 3091, a PD
3092, and a summator 3093.
The PD 3091 is configured to receive the ninth optical signal, and
convert the ninth optical signal into a fifth electrical
signal.
The PD 3092 is configured to receive the tenth optical signal, and
convert the tenth optical signal into a sixth electrical
signal.
The summator 3093 is configured to superimpose the fifth electrical
signal and the sixth electrical signal, and output the second
electrical signal. It should be noted that the superimposing may be
a subtractive operation, or may be an addition operation.
Optionally, the apparatus 300 further includes a phase demodulator
311 configured to adjust a phase of a code word of the local
oscillator optical signal such that the code word of the local
oscillator optical signal is aligned with a code word of the
received optical signal.
In this embodiment of the present disclosure, a high SNR can be
obtained by means of coherent optical receiving. In addition,
accumulation is performed only in an electrical domain, and
multiplication is transferred to an optical domain such that a chip
rate can be easily raised to 20 GHz, or even to 25 GHz. In
addition, the apparatus provided in this embodiment of the present
disclosure requires lower costs than that required in the other
approaches.
Embodiment 3
This embodiment of the present disclosure further provides a method
for despreading in an optical domain, where the method includes the
following steps.
Step S401: Split a received optical signal into a first optical
signal and a second optical signal.
Step S402: Perform field modulation on the first optical signal to
obtain a third optical signal, where a phase difference between the
third optical signal and the first optical signal is a first
difference.
Step S403: Perform phase deflection on the third optical signal and
the first optical signal to obtain a fourth optical signal and a
fifth optical signal.
Step S404: Superimpose electrical signals that are obtained by
converting the fourth optical signal and the fifth optical signal
to generate a first electrical signal.
Step S405: Accumulate the first electrical signal in a code word
period.
Field modulation is performed on the first optical signal according
to a local code word.
Optionally, a polarization direction of the first optical signal is
the same as a polarization direction of the third optical
signal.
Further, performing phase deflection on the third optical signal
and the first optical signal to obtain a fourth optical signal and
a fifth optical signal includes deflecting a phase of the third
optical signal by the first difference, superimposing the third
optical signal and the first optical signal to obtain the fourth
optical signal, deflecting a phase of the first optical signal by
the first difference, and superimposing the first optical signal
and the third optical signal to obtain the fifth optical
signal.
Further, superimposing electrical signals that are obtained by
converting the fourth optical signal and the fifth optical signal
in order to generate a first electrical signal includes converting
the fourth optical signal into a second electrical signal,
converting the fifth optical signal into a third electrical signal,
and superimposing the second electrical signal and the third
electrical signal to obtain the first electrical signal.
Optionally, the method further includes adjusting a phase of a code
word of the second optical signal such that the code word of the
second optical signal is aligned with a code word of the received
optical signal.
Preferably, the first difference is .pi./2.
Optionally, the first difference may be .pi./4, .pi./16, or
.pi./8.
Embodiment 4
This embodiment of the present disclosure further provides a method
for despreading in an optical domain, where the method includes the
following steps.
Step S501: Split a received optical signal into a first optical
signal and a second optical signal whose polarization directions
are perpendicular to each other.
Step S502: Split a local oscillator optical signal emitted by a
local oscillator laser into a third optical signal and a fourth
optical signal whose polarization directions are perpendicular to
each other.
Step S503: Modulate the third optical signal and the fourth optical
signal to generate a fifth optical signal and a sixth optical
signal.
Step S504: Perform phase deflection on the first optical signal and
the fifth optical signal, to obtain a seventh optical signal and an
eighth optical signal.
Step S505: Perform phase deflection on the second optical signal
and the sixth optical signal to obtain a ninth optical signal and a
tenth optical signal.
Step S506: Superimpose electrical signals obtained by converting
the seventh optical signal and the eighth optical signal to obtain
a first electrical signal.
Step S507: Superimpose electrical signals obtained by converting
the ninth optical signal and the tenth optical signal to obtain a
second electrical signal.
Step S508: Superimpose the first electrical signal and the second
electrical signal to obtain a third electrical signal.
Step S509: Accumulate the third electrical signal in a code word
period.
Optionally, before step S509, the method further includes
performing a square operation on the first electrical signal and
the second electrical signal.
The square operation may be completed using a digital device, such
as an ADC or an analog device.
It should be noted that the foregoing step numbers S501 to S509 are
not a limitation to a step performing sequence. For example, step
501 and step 502 may occur at the same time, or may occur in
sequence. The same is true of other steps, and a sequence of
performing the steps is not limited in the present disclosure. A
person of ordinary skill in the art may clearly obtain the present
disclosure according to a known art after learning the method
provided in the present disclosure.
Further, performing phase deflection on the first optical signal
and the fifth optical signal to obtain a seventh optical signal and
an eighth optical signal includes deflecting a phase of the fifth
optical signal by the first difference, superimposing the fifth
optical signal and the first optical signal to obtain the seventh
optical signal, deflecting a phase of the first optical signal by
the first difference, and superimposing the first optical signal
and the fifth optical signal to obtain the eighth optical
signal.
Preferably, the first difference is .pi./2.
Optionally, the first difference may be .pi./4, .pi./16, or
.pi./8.
Further, performing phase deflection on the second optical signal
and the sixth optical signal to obtain a ninth optical signal and a
tenth optical signal includes deflecting a phase of the sixth
optical signal by the first difference, superimposing the sixth
optical signal and the second optical signal to obtain the ninth
optical signal, deflecting a phase of the second optical signal by
the first difference, and superimposing the second optical signal
and the sixth optical signal to obtain the tenth optical
signal.
The superimposing electrical signals obtained by converting the
seventh optical signal and the eighth optical signal includes
converting the seventh optical signal into a fourth electrical
signal, converting the eighth optical signal into a fifth
electrical signal, and superimposing the fourth electrical signal
and the fifth electrical signal, to obtain the first electrical
signal.
The superimposing may be a subtractive operation, or may be an
addition operation.
The superimposing electrical signals obtained by converting the
ninth optical signal and the tenth optical signal includes
converting the ninth optical signal into a sixth electrical signal,
converting the tenth optical signal into a seventh electrical
signal, and superimposing the sixth electrical signal and the
seventh electrical signal, to obtain the second electrical
signal.
The superimposing may be a subtractive operation, or may be an
addition operation.
Optionally, the method further includes adjusting a phase of a code
word of the local oscillator optical signal such that the code word
of the local oscillator optical signal is aligned with a code word
of the received optical signal.
The foregoing descriptions are merely specific implementations of
the present disclosure, but are not intended to limit the
protection scope of the present disclosure. Any variation or
replacement readily figured out by a person skilled in the art
within the technical scope disclosed in the present disclosure
shall fall within the protection scope of the present disclosure.
Therefore, the protection scope of the present disclosure shall be
subject to the protection scope of the claims.
* * * * *